Science writer Brian Clegg recently wrote in his blog* that religious thinking is often "magical" thinking. He gave several examples from the Judeo-Christian tradition, including this one from the Church of England:

I would suggest that those in the Church of England who don’t want women bishops are motivated by magic. Their argument is that it has always been that way, that Jesus only chose male apostles, and that bishops sort of stand in for Jesus, so have to be male, as he was.

Clegg is a science writer, and quite a good one, but his expertise does not extend to Christian theology. His example above confuses magical thinking with sacramental thinking.

Magical thinking is "nonscientific causal reasoning" that follows certain rules, a bit analogous to scientific laws. Like scientific laws, magical thinking does not identify these rules as arising from any particular source; they just are. Superstitions arise from magical thinking.

Christianity — particularly Catholic Christianity and those Protestant traditions most akin to Catholicism — is deeply imbued with sacramental thinking. In a sacrament, there is an outward, visible symbol of a supernatural reality. In the case of ordination, the supernatural reality is that deacons, priests, and bishops are marked with a supernatural character that gives them the ability to "stand in" for Christ. The outward symbol includes the necessity that the ordained be similar to Christ in the most fundamental way: they must be male. (I think it's interesting that the Church of England is hung-up on female bishops, since it already allows female deacons and priests — doesn't it make sense that God would require male gender for either all ordinations or for none?)

Unlike magical thinking, the associations found in sacramental theology are attributed to a specific and personal source — God. Male gender is not necessary because of our limited perceptions and understanding, nor because of some great cosmic "should"; it is necessary because God made it so.

* Do not, by any means, miss the first comment to Clegg's post! It will make your day.